1. Field of the Invention
The present invention relates to a method of manufacturing a minute structure, and to a minute structure and a minute structure device manufactured by the manufacturing method. More particularly, the present invention relates to a method of manufacturing an ordered minute structure by forming a recess-projection pattern in the surface of a substrate or on the substrate by means of interference lithography, irradiation with a focused ion beam, or the like. The present invention also relates to a minute device characterized by using an orderly minute structure as a mold or a mask.
2. Related Background Art
Some thin films, wires, dots, or the like of metals and semiconductors, having a size smaller than a specific length, confine motions of electrons to exhibit a unique electrical, optical or chemical characteristic. From this point of view, there is a growing interest in minute structures of nano-sizes having a structure smaller than several hundred nanometers (also called nanostructures) as a high-performance material.
Methods for manufacturing such nanostructures include a method of directly manufacturing a nanostructure by a semiconductor processing technique, e.g., photolithography, electron beam lithography, x-ray lithography, etc. Methods of forming a very fine pattern are reported by, for example, M. C. Hutley, “Coherent Photofabrication”, Optical Engineering, Vol. 15 No. 3(1976), and J. Y. Decker et al, “Generation of subquarter-micron resist structures using optical interference lithography and image reversal”, J. Vac. Sci. Technol, B15(6), Nov/Dec(1997).
Besides the development of these manufacturing methods, trials have been made to realize novel nanostructures on the basis of orderly structures spontaneously formed, i.e., structures formed in a self-ordering manner.
As a method of such self-ordering, an anodizing method can be mentioned which enables easy controllable manufacture of a structure having nano-sized pores (nanoholes). For example, anodic alumina produced by anodizing Al or an Al alloy in an acid bath is known.
If an Al plate is anodized in an acid electrolyte, a porous oxide membrane is formed (see, for example, R. C. Furneaux, “The formation of controlled-porosity membranes from anodically oxidized aluminium”, NATURE, Vol. 337, P147(1989), etc.). Specifically, this porous oxide membrane has a unique geometric structure in which very thin cylindrical pores (nanoholes) having a diameter of several namometers to several hundred nanometers are arrayed at intervals of several namometers to several hundred nanometers (cell size).
A method of performing two anodizing steps in order to improve the verticality, linearity and independence of such pores has been proposed. In this method, a porous oxide membrane formed by anodizing is temporarily removed and is again processed by anodizing to make a porous oxide membrane having pores (Masuda et al, “Fabrication of gold nanodot array using anodic porous alumina as an evaporation mask”, Jpn. J. Appl. Phys, Vol. 35, Part 2, No. 1B, L126-L129(1996)).
Further, a method of forming pore formation start points by using a stamper in order to improve the controllability of the shape, interval and pattern of pores of a porous oxide membrane has been proposed (Japanese Patent Application Laid-Open No. 10-121292, EP-A-931859). That is, in this method, dents are formed as pore formation start points in the surface of an Al plate by pressing a substrate having a plurality of projections against the surface of the Al plate, and anodizing is thereafter performed to make a porous oxide membrane having pores. Japanese Patent Application Laid-Open No. 11-200090, and EP-A-0913850 Publication, etc. Also disclose contents relating to porous oxide membranes having pores.
Various applications of anodic alumina have been tried by considering the unique geometrical structure of anodic alumina. For example, applications to membranes utilizing the wear resistance and electric insulation of anodic oxide film, and to filters in the form of a separated membrane are known. By using a technique of filling nanoholes with a metal, a semiconductor or the like, or a nanohole replication technique, applications to coloring, magnetic recording mediums, electroluminescent elements, electrochromic elements, optical elements, solar cells, gas sensors, and other various applications are now being tried. Further, applications to quantum effect devices, such as quantum wires, and metal-insulator-metal devices, to molecule sensors using nanoholes as a chemical reaction field, and other various applications are expected (Masuda, “Highly-Ordered Nanohole-Array from Anodic Porous Alumina”, Kotaibutsuri (solid state physics), Vol. 31, No. 5, 493-499(1996)).
There is a demand for a simple method for manufacturing nano-sized structures with improved reproducibility.
However, there is a limit in terms of controllability, to the improvement of methods based on ordinary anodizing and/or there is a limit to the interval between formable pores, and the material needs to be anodized for a long time.